Losartan: uses, dosing, side effects & brands

Arbli (Losartan Potassium) is an angiotensin 2 receptor blocker used to treat Diabetic Nephropathies, Heart Failure, Hypertension, Left Ventricular Hypertrophy.

The FDA classifies losartan as an angiotensin 2 receptor blocker. Angiotensin II receptor blockers (ARBs) block the AT1 receptor that the hormone angiotensin II uses to tighten blood vessels and make the body hold onto salt and water. With that receptor blocked, vessels relax and widen, so blood pressure falls. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.

The elimination half-life of losartan is about 2 hours — that is how long the body takes to clear half of a dose. Losartan has an active metabolite (E-3174/EXP3174) with a longer terminal half-life of about 6 to 9 hours, and the FDA label states this metabolite is responsible for most of the blood-pressure-lowering effect. Half-life is not the same as how long a drug test can detect the drug, and it varies with age, kidney and liver function.

It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run losartan against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.

Across the brands we track, losartan is currently marketed as suspension, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.

We do not currently list a generic-labelled losartan product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.

The FDA's Enforcement database lists 1 recall record whose product description mentions losartan. The most recent: Losartan Potassium and Hydrochlorothiazide Tablets (May 7, 2024). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.

Losartan begins lowering blood pressure within about 6 hours, but most of the effect appears within 3 to 6 weeks of daily use. You will not feel it working; blood-pressure readings over a few weeks are how it is judged.

Food: salt substitutes containing potassium, and large amounts of potassium-rich foods or supplements — see the food section above for what each one does and whether it means avoiding it or just being consistent. This is what the FDA label and our cited sources say — it is not a complete list. Your pharmacist can check your own combination.

The most common are dizziness or lightheadedness (especially with your first doses or when you stand up quickly), tiredness, and low blood pressure. Losartan is an ARB, so unlike ACE inhibitors it rarely causes a dry cough. MedlinePlus also lists muscle cramps or weakness, back or leg pain, diarrhea, and heartburn. Rising slowly from sitting or lying down helps with the dizziness. Tell your doctor if any of these are severe or persistent.

Call for emergency help right away if you have signs of angioedema (a rare but dangerous allergic swelling). MedlinePlus says to call your doctor immediately for "swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs; hoarseness; difficulty breathing or swallowing; chest pain." Also contact your doctor for signs of high potassium (hyperkalemia) — such as muscle weakness, a slow or irregular heartbeat, or numbness/tingling — and for very low blood pressure (fainting, severe dizziness). Losartan can also affect kidney function, so report a large drop in how much you urinate.

Yes. Losartan carries the ARB class boxed warning for fetal harm. MedlinePlus states plainly: "Do not take losartan if you are pregnant," and warns that "losartan may cause death or serious injury to the fetus when taken in the last 6 months of pregnancy." If you become pregnant while taking it, "stop taking losartan and call your doctor immediately." Tell your doctor before starting the drug if you are pregnant, planning to become pregnant, or breastfeeding.

Losartan is often prescribed to protect the kidneys, but in some situations it can temporarily worsen kidney function. The risk is higher if you become dehydrated (from vomiting, diarrhea, heavy sweating, or too little fluid), take NSAID painkillers like ibuprofen or naproxen, or have narrowed kidney arteries. This is why doctors check blood tests for kidney function and potassium after starting or increasing the dose. Stay hydrated, avoid routine NSAID use unless your doctor approves, and keep your lab appointments.

Dizziness from the blood-pressure-lowering effect is most likely with your first few doses and usually eases as your body adjusts over days to a couple of weeks. Do not stop losartan on your own, even if you feel fine — MedlinePlus notes it "controls high blood pressure but does not cure it," so blood pressure can climb back up if you quit. If side effects bother you, talk to your doctor about adjusting the dose or switching, rather than stopping abruptly. This is not a complete list of side effects; ask your pharmacist or doctor about anything unusual.

Losartan is an angiotensin receptor blocker (ARB) used mainly for the heart and kidneys. Its FDA-approved uses are treating high blood pressure (hypertension), lowering the risk of stroke in people who have high blood pressure along with an enlarged heart muscle (left ventricular hypertrophy), and protecting the kidneys in people with type 2 diabetes who have high blood pressure and diabetic kidney disease (diabetic nephropathy). It relaxes blood vessels by blocking angiotensin II, a hormone that narrows them.

Both lower blood pressure by acting on the same hormone system, but losartan (an ARB) blocks angiotensin II from working, while ACE inhibitors like lisinopril block the enzyme that makes it. The practical difference for many people is side effects: ACE inhibitors commonly cause a persistent dry cough, which ARBs like losartan rarely do. For that reason, losartan is often chosen for people who can't tolerate an ACE inhibitor. Both carry a risk of raising potassium and both must be stopped in pregnancy.

These are off-label uses, not FDA-approved indications for losartan. ARBs as a class are used in heart failure, but candesartan and valsartan are the ones specifically FDA-approved for it. Losartan has also been studied and used off-label to slow enlargement of the aorta in Marfan syndrome, and to reduce protein in the urine in chronic kidney disease. Any use beyond high blood pressure, stroke prevention, or diabetic kidney disease should be directed by your doctor.